STKs (serine/threonine-protein kinases) catalyse the transfer of the gamma-phosphoryl group from ATP to serine/threonine residues on protein substrates. TTBK is a neuron-specific kinase that phosphorylates the microtubule-associated protein tau and promotes its aggregation. Higher vertebrates contain two TTBK proteins, TTBK1 and TTBK2, both of which have been implicated in neurodegeneration. Genetic variations in TTBK1 are linked to Alzheimer's disease (AD). Hyperphosphorylated tau is a major component of paired helical filaments that accumulate in the brain of AD patients []. Studies in transgenic mice show that TTBK1 is involved in the phosphorylation-dependent pathogenic aggregation of tau [, ].
